The present invention relates to carrier tapes and in particular to a reuseable carrier tape for transporting electronic components, pharmaceuticals, and the like during production and assembly operations.
In the assembly of various types of electronic devices, such as, for example, computers and related products, it is common to transport miniature and subminiature components from one station to another by means of a carrier tape. At the assembly stations automatic equipment functions to remove the components from the carrier tape and mount the components to a circuit board or the like as may be required. The carrier tape (or transfer tape as it is sometimes referred to) may also function to bring different components to an assembly station in proper order for sequential assembly. Such tapes are often formed from an elongated base strip of plastic or paper usually covered by a cover strip. The base strip is often provided with cavities which are contoured to hold the components in a particular orientation. The cover strip is usually held in place by an adhesive or heat bond which must be broken at the assembly station to permit the component to be removed after the cover is stripped back. Typical examples of prior art carrier tapes are disclosed in U.S. Pat. Nos. 3,465,874; 3,650,430; 3,700,019; 3,894,896; 3,910,410 and 4,298,120.
A problem often associated with such prior carrier tapes is that the cover sheet must be securely affixed to the base and the adhesive bond must subsequently be broken without damaging the cover sheet or base since this could interfere with the transport mechanism. In the past adhesives and heat sealing were the principal means for sealing the base and cover sheets which often rendered the base and/or cover sheet non-reuseable. In many ultra-clean applications the use of such adhesives and heat bonds is undesirable out of concern that residue may contaminate the component or mounting board. In addition, heat seal bonds are generally non-uniform due to the occurrence of tiny hills and valleys on the strip during the heating operation. This may result in the cover sheet stripping away prematurely, (which could result in lost components) or remaining in place overly long. In either event the automatic operation would be interferred with.
Also, with many electronic components it is desireable to load the carrier tape with static-dissipative or conductive materials to prevent or dissipate any build-up of electrostatic charge. These materials often tend to interfere with the bonding characteristics of the adhesives used.
In U.S. Pat. Nos. 3,465,874 and 3,650,430 an attempt is made to solve these problems by providing spaced snaps or push buttons on one of the strips to engage spaced holes in the other of the strips. This arrangement, obviously requires somewhat precise alignment of the snaps and openings in order to operate. Further, the strips are not uniformly secured to each other but rather continuously oscillate between secured and non-secured conditions.
In view of the above, it is the principal object of the present invention to provide an improved carrier tape construction in which the base and cover strips are uniformly and consistently secured to each other and which requires a uniform force for separation so that they may readily be separated in a precise manner.
A further object is to provide such a carrier tape in which the components are reuseable.
Still another object is to provide a carrier tape which may readily be used on existing equipment with little or no modification and which is competitive pricewise with existing products.